The present invention is related generally to vehicles having a single forward driven wheel and a steerable pair of rear movable supports such as wheels.
For generations, youngsters have enjoyed riding tricycles. However, the advent of low swung molded plastic three-wheeled velocipedes that place the rider below the axis of the front drive wheel have captured much of the standard tricycle market. Indeed, the standard form of tricycle has quickly become antiquated and the term "trike" is unknown to many youngsters.
The vehicles that are displacing "trikes" are both faster and maneuverable. The low center of gravity produced by placing the rider below the rotational axis of the front driving wheel also adds a considerable safety factor in that the vehicle becomes extremely difficult to roll laterally. Additional advantages to the newer vehicle forms become very apparent when one watches a youngster maneuver his "Big Wheel" (trademark) into a tight corner at high speed.
The newer, low-slung tricycle is designed specifically for youngsters, not for the adolescent-to-adult group. Adolescents must give up the vehicles they outgrow for the more "grown up" bicycle, leaving behind the thrill of scooting along inches from the ground surface.
Modern "tricycles" are not typically designed to give the rider total steering control. Bicycles, on the other hand, can be leaned into a curve to counteract centrifugal forces. It is the rider more than mechanical steering apparatus who initiates and actually produces the turning impetus. The typical tricycle, old or new, is designed with three point ground contact geometry to mechanically withstand centrifugal force without substantial assistance from the rider. When the centrifugal force overcomes the resistance produced by the tricycle geometry, the result is a sudden outward slide or roll of the vehicle and rider. The point at which centrifugal outward force overcomes the resistance offered by the tricycle occurs so quickly that it is not generally within the capability of the rider to correct or compensate by shifting his body weight into the turn.
It therefore becomes desirable to obtain a vehicle that will provide greater maneuverability than standard tricycles and that gives the rider greater control of the apparatus in turns.
The maneuverability problem briefly discussed above has been realized to a limited extent by some manufacturers of the new forms of tricycles. Some designs provide rear steering wheels that are set about a fixed incline steering axis. By doing this, the rider is able to turn the vehicle while simultaneously leaning it in the direction of turn; the sharper the turning radius, the greater the inclination into the turn. These forms of tricycles are an improvement over the fixed wheel variety, but still lack the desirable feature of adjustability for the angle of the steering axis. The rider is still not allowed total vehicular control. Steering conditions are the same regardless of the operating speed.
Some steering adjustments have been provided on "skateboards" which provide adjustable undercarriages. Steering is accomplished by the rider as he shifts his weight from one side to the other. The steering axis can be adjusted when the board is not in use through various clamp release, set screw, and other mechanical adjustment features. The difficulty remains, however, of being able to control the steering characteristics of the vehicle while the vehicle is in use.
A more substantial improvement has been developed in a vehicle having a front driver wheel and rear wheels that are steerable about a rider adjustable steering axis which is disclosed in U.S. Pat. No. 4,198,072 granted to Grant Hopkins. The steering axis, a steering control axis, and the rear wheel axis are nonintersecting and spaced apart from one another. The steering axis and wheel axis pivot about the remote steering control axis as the rider changes his posture against a pivoted backrest. The rider can change the steering response by shifting his posture between sitting and supine positions. The vehicle steering response thus varies with the angular position of the backrest. This feature enables substantial rider control but is somewhat difficult to master. Additionally, the linkage and carriage mechanism mounting the rear wheels is bulky and cumbersome, adding to the weight and overall cost of the vehicle.
The present invention represents a substantial improvement in the above described vehicle and steering mechanism by providing a compact steering control assembly with the steering axis, steering control axis and wheel axis all intersecting, preferably, with the wheel axis and steering control axis coaxial. The steering control axis is operated from hand grips on the axle and the rider sits in a constant reclining position. His torso and legs thus remain in a preferred position to enable maximum pedaling efficiency at any steering mode.